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Cells160-page15 - moved into the cytosol for use and...

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Cell - 15 Vacuoles Vacuoles are also membrane-bounded sacs that hold something (good definition). Vacuoles contain a variety of substances, such as food, wastes, water, etc. Some vacuoles are permanent structures of cells, such as those involved with water balance in protists and the central plant vacuole of plant cells. Others are temporary, such as food and waste vacuoles. We will mention three vacuoles: food vacuoles, contractile vacuoles found in protists, and the central plant vacuole. Food Vacuoles Organisms that feed by phagocytosis surround their prey item with a portion of their plasma membrane, and engulf the item by fusing the membrane around it and moving the now "food vacuole" into the cytosol. Once in the cytoplasm of the cell, the food vacuole is merged with lysosomes for digestion. Digested nutrients are
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Unformatted text preview: moved into the cytosol for use, and non-digested materials are formed into a waste vacuole that is removed from the cell by a more-or-less reverse process to the initial engulfing. Paramecium Food Vacuoles Chilodinella Food Vacuoles filled with carmine-dyed yeast containing Diatoms Contractile Vacuoles Most terrestrial organisms risk dehydration, evaporating water to their surroundings. In contrast, fresh water organisms are in an environment where water tends to move into their cells. Many fresh water protists have contractile vacuoles, structures that collect the water moving into their cell from the environment, and periodically expel the collected water to the external environment by contracting the vacuole though a pore, hence the name, contractile vacuole....
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